setOps for nodejs

Set operations in setOps.js take two arrays and return the result of the operation as an array. Supported operations are union, intersection, difference, complement, and equals. difference is the symmetric difference and complement is the relative complement. The set operations are fast, even for large arrays.

Usage

var so = setOps,
a = [1, 1, 2, 3, 3], // [1, 2, 3]
b = [3, 4, 4, 5, 5]; // [3, 4, 5]

// Join two sets together. A ∪ B
so.union(a, b); // => [1, 2, 3, 4, 5]

// The intersection of two sets. A ∩ B
so.intersection(a, b); // => [3]

// The symmetric difference of two sets. A Δ B
so.difference(a, b); // => [1, 2, 4, 5]

// The relative complement, or a minus b. A\B
so.complement(a, b); // => [1, 2]

// Set equality. A = B
so.equals(a, b); // => false
so.equals(a, [1, 2, 3]); // => true

Using Objects

Arrays of objects can be used in set operations as long as they have some type of unique identifier. If objects have a toString method which returns the unique identifier, they can be used as is. If not, a custom uid method can be specified. The methods pushUid and popUid work together to set and remove a context for returning an object's identifier.

var so = setOps,
a = [{id:1}, {id:2}],
b = [{id:2}, {id:3}],

// Push a method to retrieve object ids onto the uid stack.
uidMethod = so.pushUid(function() {
  return this.id;
});

// Peform set operations.

so.union(a, b); // => [{id:1}, {id:2}, {id:3}]

so.intersection(a, b); // => [{id:2}]

so.difference(a, b); // => [{id:1}, {id:3}]

so.complement(a, b); // => [{id:1}]

so.equals(a, b); // => false
so.equals(a, [{id:1}, {id:2}]); // => true

// Now that we're done, restore the previous uid method
// (by default an identity method).

uidMethod = so.popUid();

Installing

npm install https://github.com/rolfen/setOps.git

Testing

npm test

Credits

James Abney